Mycobacterium kansasii is one of the main mycobacterial species. Among the numerous subtypes, I and II subtypes are the only pathogens ones. A 56 years old woman has been under observation during her hospitalization for a cervical adenitis check-up; these one having been evolving for 2 months, without inflammatory syndrome. The failures of various antibiotics treatments lead one to withdraw some cervical ganglions whose histopathologic aspect reminds tuberculosis. These adenitis being isolated. An INH, rifampin, and ethambutol associated treatment is set up. After 2 weeks, the different cultures enable to isolated numerous photochromogenic colonies; a positive result is obtained with M. kansasii probe (Accuprobe). The identification is confirmed in 24 hours time with another molecular hybridation test (INNO-LiPA V2); the various specific probes of the different M. kansasii subtypes show it's not a I or II subtype (subtype IV by sequence analysis). This observation underlines the advantage and rapidity of the new diagnosis methods for nontuberculous mycobacterial diseases.